Prestressed rolling mill



July 30, 1968 Filed May '4, 1965 M. D. STONE PRESTRESSED ROLLING MILL 5Sheets-Sheet l INVENTOR. MORRIS D. STONE TORNEY y 30, 8 M. 0. STONE3,394,575

PRESTRESSED ROLLING MILLI Filed May 4, 1965 5 Sheets-Sheet 2 INVENTOR.MORRIS D. STONE BY 7%ML RNEY July 30, 1968 M. D. STONE 3,394,575

PRESTBESSED ROLLING MILL File d May 4, 1965 5 Sheets-Sheet s I (IOINVENTOR. MORRIS D. STONE HIS AT ORNEY M. D. STONE PRESTRESSED ROLLINGMILL July 30, 1968 5 Sheets-Sheet 4 Filed May 4, 1965 a 5% A w QJwINVENTOR. MORRIS D. STONE HIS ATTORNEY y 30, 1968 M. D. STONE 3,394,575

' PRESTRESSED ROLLING MILL Filed May 4, 1965 v 5 Sheets-Sheet 5 FIG. 5

INVENTOR. MORRIS D. STONE HIS ATTORNEY United States Patent 3,394,575PRESTRESSED ROLLING MILL Morris Denor Stone, Pittsburgh, Pa., assignorto United Engineering and Foundry Company, Pittsburgh, Pa., acorporation of Pennsylvania Filed May 4, 1965, Ser. No. 453,000 Claimspriority, application Great Britain, May 13, 1964, 20,009/64 13 Claims.(Cl. 72-221) ABSTRACT OF THE DISCLOSURE A rod or bar rolling mill of theprestressed type wherein the prestressed pressure is maintained greaterthan the expected rolling load and the mill is constructed to subjectthe housing, bearing chock assemblies and rolls to the prestressedpressure. In this construction the mill is provided with cooperativerigid screws-piston cylinder assemblies-the piston cylinder assembliesare employed initially and before rolling to apply the prestressedpressure and the screws are employed during rolling to apply thepressure once the piston cylinder assemblies are rendered inoperative.The rolls are provided with pressure transmitting portions which allowthe prestressed pressure to be taken directly through the rolls andconstitute the mill a closed mill. In combination with the prestressingfeature anti-roll deflection means is also provided, thereby providingan extremely rigid mill construction.

The present invention relates to a rolling mill, and, more particularly,to a rolling mill designed to roll extremely close tolerance products.

For the purpose of discussing the present invention, its use inconnection with a bar mill has been selected, although it will beappreciated that the invention may be employed in other types of mills,such as, rod mills, structural mills, etc.

Both with respect to the desire to increase the yield of the rollingmill and to meet the ever-increasing, stiffer tolerance requirements,there is present a great need for providing a rolling mill which willroll bars to one-half present standard bar tolerances or better. Such anobjective could not be obtained by conventional mills where the rollsare arranged to extend between the spacedapart housings, in view of thefact that they inherently possessed considerable mill stretch or elasticdeformation of parts and deflection of the rolls, which made itimpossible to roll products within a predetermined narrow range oftolerances.

To illustrate this, reference will be made to one type of 2-high millpreviously employed, which was designed to produce a 1 /2 diameter steelbar, wherein the final pass developed a rolling force of the order of135,000 lbs. Under this force, the inherent stretch or elasticdeformation of the composite mill structure, that is to say, theelongation of the housing posts, the bending of the top and bottomhousing separators, the compression of the mill screws, filler platesand chocks amounted to approximately .004 inch. Assuming that theparticular mill in question employed cast iron metal rolls of 12 inchdiameter by 24 inches long, under the above rolling force, each of therolls would bend or deflect about .0095 inch, the total deflectionamounting to .019 inch for both rolls. Therefore, the total mill stretchequals .023 inch which has a corresponding mill spring constant of theorder of 5,900,000 lbs. per inch. It can be seen, therefore, from thisanalysis that 17 percent of the mill stretch is traceable to the millproper, while the remaining, that is 83 percent of the mill stretch, istraceable to the rolls themselves.

This analysis demonstrates that in the type of mill under discussion thesolution to the problem of manufacturing a mill that will produce barswithin close tolerances must lie in a construction that not only willconsiderably reduce the mill stretch of the housing, 'but more importantin a construction that will in combination therewith reduce appreciablythe deflections of the rolls. The ultimate, of course, would be a millconstruction that would in addition eliminate or considerably reduce theelastic deformation of the other components of the mill, such as, thechocks and filler plates and the compression of the mill screws. Inother words, the optimum mill design would be a design that wouldgreatly increase the rigidity of the mill and its component parts,together with the elimination or substantial reduction of thedeflections of the rolls thereof.

It is an object of the present invention to provide a rolling mill,wherein the rigidity of the mill housing and the other component partsof the mill, such as the chocks, screws and filler plates are subject toa predetermined prestressing pressure greater than the largestanticipated rolling force which will eliminate the elastic deformationof these parts from influencing the gauge of the bar.

The present invention is addressed to a closed mill, that is to say, therolls are in contact with each other so that the prestressing pressureis taken directly through the rolls and, in addition to prestressingpressure being applied at the ends of the rolls in one form,prestressing pressure is applied intermediate the ends thereof.

It is also contemplated by the present invention to provide incombination with the prestressing arrangement, means for reducing themill stretch incident to the deflection of the roll or rolls. In oneform the roll deflection under rolling pressure is partly or whollyalleviated by providing crowned rolls, in which respect the rolls areprovided with a series of lands spaced across the length of the rollswhich engage each other during the operation of the mill and transmitthe prestressed pressure in the form of a closed pressure circuit. Inanother form the deflection of the roll under rolling pressure iseliminated or reduced by providing the roll with a central flatcylindrical portion, which portion outward from the rolling 'bite isengaged by a short-bodied backup roller, which is adjustable toward andaway from the roll by a pressure exerting means, such as, a pistoncylinder assembly.

In one preferred form of the present invention there is provided ahousing, including a window, a pair of metal reducing rolls having anumber of roll passes along their length and other portions thatforcefully engage each other, including central land portions, bearingsand chocks for the journals of the rolls received in the housing Window,roll adjusting means carried by said housing for positioning one of therolls relative to the other, means for prestressing the housing, bearingand chocks of the rolls and the roll adjusting means, to an extentgreater than the largest anticipated rolling force, said means forprestressing, including means for applying prestressing pressure againstsaid lands to both assist in prestressing and in resisting thedeflection of the rolls.

These features and various other advantages of the present inventionwill become more apparent when the following description is read alongwith the accompanying drawings of which:

FIGURE 1 is an outside elevational view of a bar mill illustrating oneembodiment of the present invention;

FIGURE 2 is an elevational view, partly in section, of the millillustrated in FIGURE 1;

FIGURE 3 is an enlarged view of the upper portion of the millillustrated in FIGURES 1 and 2 showing two positions of certaincomponents of the mill;

FIGURE 4 is a second modification of the prestressing cylindersillustrated in FIGURE 3, showing two positions of certain components ofthe mill; and

FIGURE 5 is an elevational view, partly in section, of a thirdembodiment of the present invention.

With reference to the drawings, reference will first be made to FIGURES1, 2 and 3 where there is shown a mill comprising two verticallyarranged, spaced-apart interconnected housings 12 and 13 having windows14 and 15 to which there is received a pair of cooperative rolls 16 and17. The rolls have a number of grooves 18, as shown in FIGURE 2, throughwhich a bar passes and is reduced in cross section. The journal portionsof the rolls 16 and 17 are received in bearings 19, which in turn arecontained in chocks 22 received in the windows 14 and 15 of thehousings. The chocks 22 of the lower roll 17 rest upon the bottom of thewindows 14 and 15, whereby the rolling forces are transmitted directlyto the lower portions of the housings 12 and 13.

As shown in FIGURE 2, which illustrates one side of the mill in section,the chocks 22 of the upper roll 16 are engaged by the lower end ofindividual screws 23, the screws being received in nuts 24 mounted inthe upper part of the housings and rotated by motors 25 through aworm-wheel set only generally shown. As FIGURE 3 shows, the top of thechocks have recesses 26 into which the lower ends of the screws extend.Cylindrical blocks 27 are also received in the recesses. Between thescrews and chocks in the usual manner, there are provided breaker blocks28.

As best shown in FIGURE 3, the upper surface of each of the blocks 27 isengaged by the lower end of a piston 29, it being noted that the nut 24is provided with a cylindrical opening 31 which forms a single actioncylinder into which the piston 29 is received. Also shown in FIGURE 3,the upper end of each cylinder has a port 32 which communicates with apassageway 33 formed in the housing, the passageway being connected to afluid supply source not shown.

Returning to FIGURE 2, each of the rolls 16 and 17 is provided with aseries of lands 34, 35 and 36, the lands 34 and 36 being arranged at theends of the rolls whereas the lands 35 are arranged at the centers andare appreciably wider than the end lands. As indicated in FIG- URE 2 andas previously noted, the lands of each roll are in contact with eachother which characterizes the mill a closed mill. In engagement with thelands 35 of the rolls are narrow-bodied, freely rotatable backup rollers37 which, on occasion are referred to as anti-deflection rollers, thebackup rollers being rotatably mounted on non-rotating shafts 38 bybearings 39, the ends of the shafts 33 being received in U-shaped yokes41 which are guided in the housings 12 and 13 in a vertical direction.At the one end of each yoke there is provided a pressure block 42, theupper surface of which is engageable by the one end of a verticallyarranged variable pressure piston cylinder assembly 43. The pistoncylinder assemblies 43, in turn, are mounted in the separators 44 thatconnect the housings 12 and 13 at the top and bottom together.

The upper narrow body roller 37, as shown in FIG- URE 1, is urgedupwardly by a balance mechanism comprising a cross bar 45, the ends ofwhich are connected to rods 46. The upper ends of the rods 46 areassociated with piston cylinder assemblies or springs 47.

One other characteristic of the mill illustrated in FIG- URES 1 and 2should be noted. As shown in FIGURE 2, as to one side of the mill,extending between the base of the housings 12 and 13 and passing throughthe window 14 is a shelf 48. The lower portion of the shelf rests on thehousings. In the vicinity of each lower chock 22, a block 49 is providedhaving at its upper end a' rocker plate 51, which contacts a similarrocker plate 52 secured to the chock 22 having its lower end formed withan inclined surface. In contact with the inclined surface of the block49 is a wedge 53 being of suflicient height to give the necessaryvertical displacement of the block 49 and chock 22. While notparticularly shown in the drawings, the block and wedge areinterconnected by an interfitting connection, such as a T slotconstruction.

The one end of the wedge 53 is provided with a threaded opening intowhich is received a screw 54. The other end of the screw 54 is formedwith two spaced collars and between which is received a bearing 55. Theouter end of the screw is formed with a nut, whereby the screw can berotated by a hand wrench, not shown. By this mechanism the pass-line ofthe mill can be maintained at a predetermined location even though therolls are turned down, and at the same time allowing the prestresspressure to pass through the blocks 49 and wedges 53 and into thehousings.

The operation of the illustrated mill in FIGURES 1 and 2 will now bebriefly explained. As previously noted the rolls are always inengagement with each other, that is to say, the lands 34, 35 and 36contact each other. Prior to the rece tion of the bar, the variablepressure piston cylinder assemblies 29 will be operated to subject thehousings 12 and 13, bearings 19, chocks 22, and also the rolls 16 and 17themselves to a prestressed pressure which at all times will becontrolled to exceed the expected rolling pressure. In addition to theprestressing pressure being supplied by the piston cylinder assemblies43, part of the pressure is supplied by the variable pressure pistoncylinder assemblies 43 which urge the antideflection rollers 37 intoengagement with the rolls 16 and 17 and which also serve to prevent anydeflection of the rolls 16 and 17. The arrows in FIGURE 2 illustrate theapplication of the pressures. After the rolling mill has beenprestressed in the aforesaid manner, the screws 23 are prestressed bybeing brought into engagement with the prestressed chocks 22 of the roll16. Once this has been performed, the pressure in the cylinders 29 willbe relieved. By using the screws in this manner a very rigidconstruction is provided and the prestressing condition of the mill isnot subject to any losses in the hydraulic system or with providing asystem to make up for hydraulic losses.

Thus, the present invention provides an extremely rigid mill wherein thetotal rigidity of the mill is many times greater than that ofconventional mills.

FIGURE 4 illustrates another embodiment of a piston cylinder assemblyprovided for prestressing the components of the mill, in which regardthere is provided on either side of the screw 23 a pair of pistoncylinder assemblies 56 having pistons 57 that engage projections 58formed on the upper chock 22 of the upper roll 16.

FIGURE 5 relates to a third embodiment of the present invention. In thisembodiment the deflection of the rolls 59 and 61 is compensated for byforming the contour of the rolls with a machine crown. In this case theends of the rolls 59 and 61 are provided with lands 62 and 63 andintermediate each groove 64 other lands 65 are formed. The land, asshown, engages the complementary lands of the other roll and transmitthe prestress pressure of the piston 29 in a closed circuit through themill as previously described and as indicated by the arrowed lines shownin FIGURE 5.

In accordance with the provisions of the patent statutes, I haveexplained the principle and operation of my invention and haveillustrated and described what I consider to represent the bestembodiment thereof. However, I desire to have it understood that withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

1. In a rolling mill comprising a housing having a window for receivinga pair of cooperative metal reducing rolls said rolls each having acentral body portion and opposite neck portions,

said central body portion of each roll having a number of complementarycooperative pass openings formed along their lengths and havingcomplementary cooperative pressure transmitting portions adjacent tosome of said pass openings, the pressure transmitting portion of oneroll being constructed to engage during rolling the complementarycooperative portion of said other roll and adapted by this constructionto transmit pressure from one roll to the other,

bearing chock assemblies mounted on the opposite ends of the. rolls andreceived in said window of said housing,

means carried by said housing for generating a prestressing pressuregreater than the largest anticipated rolling force developed betweensaid rolls,

said means being arranged with reference to said rolls,

housing and bearing chock assemblies so that the prestressing pressureis being transmitted by one roll to the other roll by said pressuretransmitting portions and said rolls, housing, bearing chock assembliesare all subject to said prestressing pressure.

2. In a rolling mill according to claim 1, wherein said prestressingmeans includes means for applying said prestressing pressure to the endsand centers of the rolls.

3. In a rolling mill according to claim 1, including means forcompensating for the deflection of the rolls under the rolling force,and

including means for adjusting one of the rolls relative to the otherwherein said adjusting means falls within said closed pressure circuitand is also subject to the prestressing pressure.

4. In a rolling mill according to claim 3, wherein the deflection of therolls is compensated for by crowning the rolls whereby in deflectiontheir pressure transmitting portions will be substantially flat.

5. In a rolling mill according to claim 3, wherein said rolls includecentral contact portions, and means -for engaging the contact portionsof the rolls to resist their deflection under the rolling forces.

6. A rolling mill according to claim 5, wherein said contact portions ofsaid rolls comprise flat lands formed on said rolls,

the engaging means comprising for each reducing roll a narrow-bodiedbackup roll arranged to engage the lands,

means for supporting the narrow-bodied backup roll,

and means for urging the backup roll towards the reducing rolls.

7. In a rolling mill according to claim 6, wherein said urging meanscomprises piston cylinder assemblies.

8. In a rolling mill according to claim 3, wherein said rollingadjusting means comprises a rigid member, means for bringing said rigidmember into engagement with the chocks of the adjustable roll when saidprestressing force has been applied, to hold the chocks of theadjustable roll in their prestressed position after which the pressuregenerating means can be released.

9. In a rolling mill according to claim 8 wherein said rigid membersinclude a pair of screws arranged to engage the chocks of the uppermostroll of said rolls,

said means for generating the prestressing pressure arranged adjacent tosaid screws and comprising at least a single piston cylinder assemblyfor each screw engagea-ble with the chocks of the uppermost roll toexert a prestressing pressure thereon.

10. In a rolling mill according to claim 9, wherein said prestressingpiston cylinder assemblies are formed in the housing and concentric withthe screws, and wherein the pistons thereof extend around the screws,the lower end of the screws passing through the cylinders of said pistoncylinder assemblies.

11. In a rolling mill according to claim 9, wherein for each screw thereis provided at least two separate piston cylinder assemblies, the pistoncylinder assembly of each pair being diametrically opposite each otherand equal distant from the screw with which they are associated andengageable with the adjacent chock of the uppermost roll.

12. In a rolling mill according to claim 1, including means for engagingthe chocks of the roll not engaged by said roll adjusting means toposition this roll relative to the pass line of the mill.

13. In a rolling mill according to claim 12, wherein said means forpositioning the roll relative to the pass line of the mill includes abeam extending between the chocks of the lowermost roll, a pair ofWedges between each chock and the beams,

means for moving one of said wedges of each pair in a first direction toimpart movement of the other wedge of each pair in a second directionthereby to move the lowermost roll towards and away from said pass line.

References Cited UNITED STATES PATENTS 774,03 5 11/ 1904 Bunton 72-2211,935,091 11/1933 Iversen 72245 2,430,410 11/ 1947 Pauls 72245 2,985,0425/ 1961 Talbot 72243 3,247,697 4/ 1966 Cozzo 72240 CHARLES W. LANHAM,Primary Examiner. A. RUDERMAN, Assistant Examiner.

